The substitution of the biologically more active thyroid hormone liothyronine for the less active thyroid hormone levothyroxine is commonly employed during thyroid hormone withdrawal in preparation for diagnostic and therapeutic interventions on thyroid cancer patients. Nevertheless, data on the liothyronine for levothyroxine therapeutic substitution are limited at the present. This prompted us to characterize the therapeutic equivalence of liothyronine and levothyroxine in a collaborative randomized, double-blind, cross-over intervention study of 10 patients whose thyroid gland has been surgically removed (i.e., had thyroidectomy). Using a variety of thyroid function tests, therapeutic substitution of liothyronine for levothyroxine was found to be achieved at an approximately 1:3 ratio. Thyroid hormones play an important role in the modulation of energy metabolism by regulating the rate of thermogenesis, i.e. the amount of heat produced to maintain the stable core temperature of the organism. In a collaborative randomized, cross-over study, we continued to analyze changes in thyroid hormones, energy expenditure and stress hormones in response to exposure to mild changes in environmental temperature using a metabolic chamber (a well-sealed chamber with tight temperature control). The results gathered from this study are expected to provide a comprehensive insight into the mechanism(s) regulating the energy metabolism in response to mild cold. They may lead to characterization of a population of subjects who require excessive energy expenditure to prevent hypothermia upon cold exposure. Osteoporosis is a major public health threat. Multiple studies have reported an association between depression and low bone mineral density, but a causal link between these two conditions is disputed. Recently, we reviewed the endocrine and immune alterations secondary to depression that might affect bone mass. Based on the evidence, we propose that depression induces bone loss and osteoporotic fractures, primarily via specific immune and endocrine mechanisms, while poor lifestyle habits and use of specific antidepressants are potential contributory factors.